Research Article: Oral Candida administration in a Clostridium difficile mouse model worsens disease severity but is attenuated by Bifidobacterium

Date Published: January 15, 2019

Publisher: Public Library of Science

Author(s): Wimonrat Panpetch, Naraporn Somboonna, Matanee Palasuk, Pratsanee Hiengrach, Malcolm Finkelman, Somying Tumwasorn, Asada Leelahavanichkul, Stephanie Diezmann.


Gut fungi may influence the course of Clostridium difficile infection either positively or negatively for the host. Fungi are not prominent in the mouse gut, and C. albicans, the major human gastrointestinal commensal yeast, is in low abundance or absent in mice. Bifidobacterium is one of the probiotics that may attenuate the severity of C. difficile infection. Inflammatory synergy between C. albicans and C. difficile, in gut, may provide a state that more closely resembles human infection and be more suitable for testing probiotic effects. We performed fecal mycobiota analysis and administered C. albicans at 1 day prior to C. difficile dosing. Fecal eukaryotic 18S rDNA analysis demonstrated the presence of Ascomycota, specifically, Candida spp., after oral antibiotics, despite negative fecal fungal culture. C. albicans administration enhanced the severity of the C. difficile infection model as determined by mortality rate, weight loss, gut leakage (FITC-dextran assay), and serum and intestinal tissue cytokines. This occurred without increased fecal C. difficile or bacteremia, in comparison with C. difficile gavage alone. Candida lysate with C. difficile increased IL-8 production from HT-29 and Caco-2 human intestinal epithelial cell-lines. Bifidobacterium attenuated the disease severity of the C. difficile plus Candida model. The reduced severity was associated with decreased Candida burdens in feces. In conclusion, gut C. albicans worsened C. difficile infection, possibly through exacerbation of inflammation. Hence, a mouse model of Clostridium difficile infection with C. albicans present in the gut may better model the human patient condition. Gut fungal mycobiome investigation in patients with C. difficile is warranted and may suggest therapeutic targets.

Partial Text

Clostridium difficile, an anaerobic spore-forming gram-positive bacterium, is the most common cause of nosocomial antibiotic-associated diarrhea of patients in long term care facilities world-wide [1, 2]. C. difficile-associated infection is also the most common hospital-acquired diarrhea worldwide [1]. Gut microbiota alteration due to antibiotic administration diminishes pathogen colonization resistance and is a well-known risk factor for C. difficile infection [2, 3]. Interestingly, C. difficile-induced GI leakage is characterized by i) spontaneous bacteremia deriving from the intestinal microbiota [4], ii) fluorescein isothiocyanate-dextran (FITC-dextran) translocation and iii) elevated serum (1→3)-β-D-glucan (BG) without fungemia [5]. The detection of dextran, a carbohydrate molecule that is not absorbed through the intestine, in serum after oral administration, is a standard gut leakage measurement method [6]. BG is a polyglucoside that is a major component of the fungal cell wall [7]. Spontaneous BG elevation in serum, in the absence of invasive fungal disease or iatrogenic contamination, is also an indirect indicator of gut leakage [5, 8]. C. difficile toxins are responsible for intestinal barrier damage through the disruption of actin cytoskeleton and tight junctions of gut epithelial cells, thus potentiating the translocation of BG [9]. Further, prolonged antibiotic administration, an important risk factor for C. difficile infection, has been shown to induce the overgrowth of Candida spp. (a ubiquitous human GI commensal organism), potentially enhancing the burden of translocatable BG [2, 3, 10, 11]. Although Candida overgrowth is well studied in humans, Candida spp. are not the predominant fungi in the murine GI tract [12]. Yamaguchi et al. demonstrated that Candida albicans in mouse feces was detectable only after a specific mouse chow administration [11]. We also demonstrated that fecal Candida is undetectable in mice without oral administration [8, 13]. Interestingly, Candida colonization has been demonstrated to alter the course of several mouse models of sepsis and food allergy [8, 13, 14]. Accordingly, Candida presence in mouse gut might have an impact on several animal models, especially with respect to intestinal inflammation, and the Candida colonization mouse model might more closely resemble human patient conditions. Based upon the role of C. difficile in enhancing intestinal permeability, and the role of BG as a pro-inflammatory pathogen-associated molecular pattern (PAMP) with pro-inflammatory synergy with other PAMPS [15, 16], we investigated the role of introduced C. albicans, and derivatives, upon the course and symptom severity of murine C. difficile infection.

Candida albicans is not a prevalent gastrointestinal microorganism in mouse. Oral challenge with Candida exacerbated several markers used to characterize the severity of the course of a C. difficile infection in a murine model. Oral-administration of C. albicans prior to C. difficile administration enhanced the disease severity through increased gut inflammation. Given that gut Candida spp. are commensal organisms in humans and are observed to experience large increases in number under the influence of a wide variety of antibiotics, the murine model of C. difficile with C. albicans might more closely resemble human conditions.

The presence of C. albicans in gut enhanced the severity of a murine C. difficile infection model, through the enhancement of intestinal inflammation. This work informs pre-clinical model development for the study of C. difficile infection and suggests translational research approaches.




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